X86 is the name of a processor instruction set, or collection of operations that a processor is able to perform. These instructions include mathematics and logic calculations, among other types of tasks. Nearly every processor in use today maintains compatibility with the x86 instruction set, which is now more than 30 years old.
The first processor to support the x86 instruction set was the Intel 8086, released in 1978. The 8086 was popular for use in personal computers in the 1980s and was used, along with chips compatible with it, in certain machines manufactured by IBM as well as "clone" computers that were compatible with IBM PCs. As Intel released new processors that were faster, compatibility with the x86 instruction set was maintained so that computer users could buy new machines without having to buy all new software as well. Although new instruction sets have since been introduced to augment x86, modern processors still retain backward compatibility with the first x86 processors.
It was not always the case that x86 processors were present in virtually all computers. Before compatibility with the IBM PC became a universal standard, many types of processors were used. The Commodore 64 and Apple II used processors made by MOS Technology, and the original Macintosh and Atari ST used processors by Motorola. None of these was x86-compatible. However, the IBM PC and its clones eventually grew to dominate the market.
Over the years, many processor manufacturers have entered the x86 market to compete head-on with Intel. Replication of the x86 instruction set was accomplished through reverse engineering, a process by which a chip's capabilities are reproduced by engineers who have no experience with the chip itself, and thus cannot steal its technology. The best known x86 processor manufacturer aside from Intel is AMD, which competes with Intel in the server, desktop and notebook processor markets.
Several extensions have been added to the x86 instruction set, with names such as MMX, SSE and 3DNow. These extensions can add a great deal of performance to a processor, because they allow the processor to spend less time waiting for orders. Rather than waiting for an instruction, completing it, then waiting for another, these new "single instruction, multiple data" instructions would cram several operations into one instruction. X86 extensions have greatly contributed to the longevity of the instruction set.
Maintaining backward compatibility with the 8086 has allowed Intel to sell a steady stream of processors, as consumers do not have to lose access to their old software to receive a speed boost from a new CPU. However, this has also hampered processor advancements in some ways. If consumers were able to tolerate purchasing new software, processor manufacturers could abandon the 30-year-old x86 instruction set and focus on the fastest new instruction set possible with current technology, making processors far faster than what is available.
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